The present invention relates to vehicle body closure panels, and more particularly to a tailgate lift assist counterbalancing hinge assembly that can be retrofitted to a vehicle's tailgate.
Vehicle body closure members, such as a tailgate, are pivotally mounted between body side panels forming the pillars at the rear of the vehicle. The tailgate pivots about a hinge axis between a horizontal, open position, and a vertical, closed position. Preferably, the mounting assemblies for the tailgate permit the tailgate to be removed, and this has been accomplished in a known construction when the tailgate is pivoted to a position between the fully open or fully closed positions. For example, the tailgate may include hinge pins that extend outwardly along the hinge axis that removably connect into brackets carried on the truck body. When the tailgate is pivoted to a predetermined intermediate position, for example, 15° away from a fully closed position, at least one of the hinge pins slips through a slot in the connecting bracket as the tailgate is lifted at one end from the truck body.
Some of the tailgate mounting assemblies include a spring bias assist for assisting movement and counterbalancing the weight of a tailgate during opening or closing movements. One previously known mechanism, in which a torque rod provides spring biasing between the tailgate and the body panel pillars, carries the torque rod on assemblies that form the pivots for the tailgate. Since the torque rod forms a portion of the pivot assembly, the torque rod must be installed for the tailgate to pivot and thus complicates the assembly procedure. Moreover, the torque rod may require particularly configured ends that complicate production of the parts before assembly.
A previously known tailgate may use hinge pin trunions for pivoting, and the torque rod is preformed and installed into the tailgate in a complex and intricate procedure. For example, during assembly of the tailgate, the stationary end of the rod has to be aligned with an aperture that exposes the end for attachment outside of the tailgate while the anchoring end is aligned with a reinforcement plate located inside the tailgate. All of the aligning must be performed while the torque rod is carried within the interior of the tailgate and the procedure may be difficult and time consuming. Moreover, numerous components are required to assemble the torque rod to the tailgate. Other types of springs used in place of the torque rod are difficult to install within the confines of tailgates made of inner and outer panels joined together before the hinge assembly is mounted. Moreover, such assemblies may be difficult to repair and replacement parts are complex and expensive.
Some vehicles are manufactured with tailgate mounting assemblies that do not include a mechanism for assisting movement by counterbalancing the weight of the tailgate during opening or closing movements. A vehicle may be ordered without a lift assist mechanism because the person buying the vehicle may not be able to afford, or maybe unwilling to pay, the additional cost of adding the lift assembly mechanism at the time the vehicle was purchased, or because the buyer simply did not appreciate the effort required to raise and lower a tailgate that can be heavy, and thus hard to lift or move when being closed or opened. In time, the vehicle operator may come to regret his or her decision to buy the vehicle without the lift assist mechanism. The present invention solves this problem by providing a simplified tailgate lift assist counterbalancing hinge assembly that can be retrofitted to the exterior of an existing vehicle tailgate.